Conventionally, in splitting a stone, a large number of boring holes are formed in a surface of the stone along the stone splitting direction, expanding members which are mounted on a distal end of a crusher are inserted into the respective holes so as to expand the boring holes in the lateral direction whereby the stone is cracked from the inside thus splitting the stone. Such a crusher is configured to perform the crushing operation in a state that left and right expanding members are mounted on a lower portion of a hydraulic cylinder in a state that the expanding members are expandable in the lateral direction, and a wedge which is arranged between the expanding members is downwardly moved by a piston rod of the cylinder thus expanding the expanding members.
Here, in the crushing structure of the left and right expanding members of the crusher, tapered surfaces are formed on the wedge toward the distal end direction from a proximal end portion, a wedge body portion having a parallel straight shape is arranged between respective tapered portions, and tapered surfaces which are equal to the tapered surfaces formed on distal end portions of the wedge are formed on inner surfaces of distal end portions of the left and right expanding members which sandwich both sides of the wedge.
Accordingly, when the wedge is lowered due to the hydraulic cylinder, the tapered surfaces of the wedge expand the left and right expanding members outwardly thus forcibly expanding the boring hole formed in the stone so as to perform the stone splitting (see Japanese Patent Laid-open Hei3 (1991)-57553).
However, the conventional crushing structure of the crusher has following drawbacks.
That is, the crusher forms the tapered surfaces which are spearheaded toward the distal end portion and have the same inclination on a proximal end portion and a distal end portion of the wedge, the distal end portions of the left and right expanding members form the tapered surfaces having the same shape as the tapered surfaces of the distal end portions of the wedge, and the expanding members are expanded by the elevation and the lowering of the wedge. Accordingly, in splitting the stone, a large number of boring holes are formed in a large stone at a fixed interval on a straight line, the expanding members mounted on the distal end of the crusher are inserted, and the wedges are downwardly moved thus collectively performing the expansion of the left and right expanding members whereby the stone is split. In such a stone splitting operation, however, at the time of expanding the expanding members, a hollow space is formed between the paralleled straight portions of the wedge body portion and inner surfaces of the expanding members and hence, the expanding force of the tapered portion of the wedge is not transmitted to the whole expanding members, that is, the expanding force is dispersed thus giving rise to a drawback that a large crushing force cannot be obtained.